1. Field of the Invention
The invention relates to an optical scanner, and more particularly, to an optical scanner with a focus adjusting system for adjusting its focus.
2. Description of the Prior Art
Prior art optical scanners usually comprise a scanning module with a fixed optical lens and light sensor for scanning a document in a fixed focus. It does not cause any problem if the resolution of the document image is not a great concern such as a text document. However, if the resolution of a document image is very important such as an artistic drawing or a color picture, a prior art scanner can not adapt its focus to capture the document image clearly since its focus is fixed. Many details of the document may be lost in such a document scanning.